The present application relates to a flow measuring system for flowing liquids under pressure, such as in pipelines and the like, more particularly, it relates to such a flow measuring system employing a manometer and a pitot rod having at least two orifices and wherein upset or temporary inversion of the manometer will not result in backflow of any indicating liquid into the primary liquid carrying pipeline.
In measuring and determining values of mean velocity and total flow in liquid carrying pipelines and the like, there are usually employed pitot rods having at least two isolated orifices of equal size, generally located at 180.degree. from each other. These pitot rod orifices are usually connected by means of fixed and/or flexible tubing to a manometer, pressure guage or pressure differential recorder. The manometer is among the most accurate because of its direct-reading nature.
Manometers generally employ liquids, usually colored by dyes, which are not soluble or miscible with the flowing liquid being measured, such as water, to enable accurate meniscus readings to be taken and recorded. These indicating liquids are generally heavier than the liquid being measured such as water, in contrast to butane, gasoline, benzene and other hydrocarbon liquids which are lighter than water and they are also immiscible with the liquid being measured in contrast to the lower alcohols such as methanol and ethanol which are fully miscible with water. Useful indicator liquids include carbon tetrachloride, tetrachloroethane, trichloroethylene and the like.
During use it is possible for a manometer to fall over or even to be inverted. When this happens the heavier liquid used as indicator liquid can flow back into the pipeline in which the velocity and flow of a liquid is being determined. This is to be avoided because some of the indicator liquids used are toxic or may be carcinogenic and thus their total exclusion from such flowing liquids as potable water supplies is highly desirable.
To avoid the above difficulties a manometer flow measuring system has been developed which insures against any possible backflow of manometer indicating liquid into the pipeline in which flow is being measured. The entire assembly is comprised of a pitot rod having at least two orifices, a manometer, two snubber vessels and connecting tubing and valves. The assembly is employed to determine flow velocities and flow volumes of flowing liquids in a pressurized conduit, part of a pressurized system of liquid transport and/or distribution. Generally, those pressurized systems in which contamination by such heavier liquids is to be most carefully avoided are potable water distribution systems for municipalities or the like.
Accordingly it is a principal object of the present invention to provide a flow measuring system that will prevent the backflow of heavier liquids into a pressurized liquid flowing in a conduit.
Another object of the present invention is to provide such a flow measuring system wherein the added novel members are easily integrated with other parts thereof.
Another object of the present invention is to provide a flow measuring system which is durable and not easily damaged.
Still another object of the present invention is to provide snubbing vessels which act to prevent backflow of heavier liquids therethrough.